There are also a lot of "intermediate length" lenses that are constructed like "normal" lenses. Most 35mm users equate "telephoto" with "longer than 50mm", but many lenses up to about 200mm are really normal lenses. All they need to be MF (or sometimes LF) lenses is a hacksaw to remove the rear half. Sometimes not even that - the Leitz 135mm Hektor simply unscrews. What you're left with is an extension tube, and a 135mm Tessar-type lens in helical focusing mount.